posix: Fix system error return value [BZ #25715]

It fixes 5fb7fc9635 when posix_spawn fails.

Checked on x86_64-linux-gnu and i686-linux-gnu.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

(cherry picked from commit f09542c584)

NEWS

@@ -46,6 +46,7 @@ The following bugs are resolved with this release:
   [25487] sinl() stack corruption from crafted input (CVE-2020-10029)
   [25523] MIPS/Linux inline syscall template is miscompiled
   [25635] arm: Wrong sysdep order selection for soft-fp
+  [25715] system() returns wrong errors when posix_spawn fails
 
 
 Version 2.30

stdlib/tst-system.c

@@ -17,14 +17,128 @@
    <http://www.gnu.org/licenses/>.  */
 
 #include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <signal.h>
+#include <paths.h>
 
+#include <support/capture_subprocess.h>
+#include <support/check.h>
+#include <support/temp_file.h>
+#include <support/support.h>
+
+static char *tmpdir;
+static long int namemax;
+
+static void
+do_prepare (int argc, char *argv[])
+{
+  tmpdir = support_create_temp_directory ("tst-system-");
+  /* Include the last '/0'.  */
+  namemax = pathconf (tmpdir, _PC_NAME_MAX) + 1;
+  TEST_VERIFY_EXIT (namemax != -1);
+}
+#define PREPARE do_prepare
+
+struct args
+{
+  const char *command;
+  int exit_status;
+  int term_sig;
+  const char *path;
+};
+
+static void
+call_system (void *closure)
+{
+  struct args *args = (struct args *) closure;
+  int ret;
+
+  if (args->path != NULL)
+    TEST_COMPARE (setenv ("PATH", args->path, 1), 0);
+  ret = system (args->command);
+  if (args->term_sig == 0)
+    {
+      /* Expect regular termination.  */
+      TEST_VERIFY (WIFEXITED (ret) != 0);
+      TEST_COMPARE (WEXITSTATUS (ret), args->exit_status);
+    }
+  else
+    {
+      /* status_or_signal < 0.  Expect termination by signal.  */
+      TEST_VERIFY (WIFSIGNALED (ret) != 0);
+      TEST_COMPARE (WTERMSIG (ret), args->term_sig);
+    }
+}
 
 static int
 do_test (void)
 {
-  return system (":");
+  TEST_VERIFY (system (NULL) != 0);
+
+  {
+    char cmd[namemax];
+    memset (cmd, 'a', sizeof(cmd));
+    cmd[sizeof(cmd) - 1] = '\0';
+
+    struct support_capture_subprocess result;
+    result = support_capture_subprocess (call_system,
+					 &(struct args) {
+					   cmd, 127, 0, tmpdir
+					 });
+    support_capture_subprocess_check (&result, "system", 0, sc_allow_stderr);
+
+    char *returnerr = xasprintf ("%s: 1: %s: not found\n",
+				 basename(_PATH_BSHELL), cmd);
+    TEST_COMPARE_STRING (result.err.buffer, returnerr);
+    free (returnerr);
+  }
+
+  {
+    char cmd[namemax + 1];
+    memset (cmd, 'a', sizeof(cmd));
+    cmd[sizeof(cmd) - 1] = '\0';
+
+    struct support_capture_subprocess result;
+    result = support_capture_subprocess (call_system,
+					 &(struct args) {
+					   cmd, 127, 0, tmpdir
+					 });
+    support_capture_subprocess_check (&result, "system", 0, sc_allow_stderr);
+
+    char *returnerr = xasprintf ("%s: 1: %s: File name too long\n",
+				 basename(_PATH_BSHELL), cmd);
+    TEST_COMPARE_STRING (result.err.buffer, returnerr);
+    free (returnerr);
+  }
+
+  {
+    struct support_capture_subprocess result;
+    result = support_capture_subprocess (call_system,
+					 &(struct args) {
+					   "kill -USR1 $$", 0, SIGUSR1
+					 });
+    support_capture_subprocess_check (&result, "system", 0, sc_allow_none);
+  }
+
+  {
+    struct support_capture_subprocess result;
+    result = support_capture_subprocess (call_system,
+					 &(struct args) { "echo ...", 0 });
+    support_capture_subprocess_check (&result, "system", 0, sc_allow_stdout);
+    TEST_COMPARE_STRING (result.out.buffer, "...\n");
+  }
+
+  {
+    struct support_capture_subprocess result;
+    result = support_capture_subprocess (call_system,
+					 &(struct args) { "exit 1", 1 });
+    support_capture_subprocess_check (&result, "system", 0, sc_allow_none);
+  }
+
+  TEST_COMPARE (system (":"), 0);
+
+  return 0;
 }
 
-
+#include <support/test-driver.c>
-#define TEST_FUNCTION do_test ()
-#include "../test-skeleton.c"

sysdeps/posix/system.c

@@ -97,7 +97,8 @@ cancel_handler (void *arg)
 static int
 do_system (const char *line)
 {
-  int status;
+  int status = -1;
+  int ret;
   pid_t pid;
   struct sigaction sa;
 #ifndef _LIBC_REENTRANT
@@ -140,14 +141,14 @@ do_system (const char *line)
   __posix_spawnattr_setflags (&spawn_attr,
 			      POSIX_SPAWN_SETSIGDEF | POSIX_SPAWN_SETSIGMASK);
 
-  status = __posix_spawn (&pid, SHELL_PATH, 0, &spawn_attr,
+  ret = __posix_spawn (&pid, SHELL_PATH, 0, &spawn_attr,
-			  (char *const[]){ (char*) SHELL_NAME,
+		       (char *const[]){ (char *) SHELL_NAME,
-					   (char*) "-c",
+					(char *) "-c",
-					   (char *) line, NULL },
+					(char *) line, NULL },
-			  __environ);
+		       __environ);
   __posix_spawnattr_destroy (&spawn_attr);
 
-  if (status == 0)
+  if (ret == 0)
     {
       /* Cancellation results in cleanup handlers running as exceptions in
 	 the block where they were installed, so it is safe to reference
@@ -182,6 +183,9 @@ do_system (const char *line)
     }
   DO_UNLOCK ();
 
+  if (ret != 0)
+    __set_errno (ret);
+
   return status;
 }